Herbaceous plants struggling with drought: Metabolic characterization of genotypic variance via NMR

Background/Question/Methods

Drought costs for ecosystem and crop productivity are a worldwide problem with climate models predicting an increase in the frequency of drought events during the next decades. Despite years of quantifying drought response from cell to ecosystem scales, drought damage assessment is still tricky because dehydration conditions induce complex alterations in plant physiology. The mechanism of carbon starvation, in conjunction with the possible desiccation caused by a failure in water transport, is the macroscopic consequence of a cascade of reactions that starts in plant cells. Water deficiency generates reactive oxygen species that negatively affect pigment concentration and increase abscissic acid (ABA). Moreover, the lack of balance between plant growth and photosynthesis rate during drought results in an initial surplus of Non Structural Carbohydrates (NSC) which likely serve as a further stress signal. Since the internal, circadian clock modulates the alterations in plant physiology induced by drought, two Brassica rapa lines that vary in circadian period and inbred lines from their crossing will be analyzed under drought. We propose the use of Nuclear Magnetic Resonance (NMR) as a fast and simple method for analyzing drought consequences on plant metabolism. NMR is a powerful method for metabolomics analyses and allows the analyses of pigments, NSC and secondary metabolites which when combined with standard measurement of plant drought responses such as leaf gas exchange and growth, will provide a full test of metabolism responses to drought.

Results/Conclusions

Under well watered conditions, the ¹H spectra suggest that the two lines have different concentrations in the lipid fraction even when exposed to the same environment. In particular, specific carotenoids signals, as lutein and carotene, concentrated between 4 and 7 ppm on the spectra, are more intense for the longer circadian period genotype compared to the shorter. Similarly, the net photosynthesis rate is higher for the genotype with a longer period. The combination of leaf gas exchange and NMR spectra shows the coordination of plant metabolism for drought. Our results from controlled drought conditions will improve predictive understanding of plant responses to increasing probability of drought as climate change occurs.